Hardnesszone indication.
Plants without a hardnesszone indication can be considered as suitable fot the Dutch climat.
Non-100% Winter-proof plants are usually indicated with a hardnesszone, as established by professionals.
However, the hardnesszones mentioned can not be taken as quarantee. It is well possible that a 'Zone-7 plant' survives a -20ºC Winter,
while the same plant might perish during a
-10ºC Winter. External influences like wind, humidity, Winter sun and the duration of cold spells may always cause problems.
The zones given here -with their approximate temperatures- are, therefor, indications only.